| 摘要 |
<p>PURPOSE:To realize the exclusive line not using DC loop system by controlling the line with two tone signals. CONSTITUTION:When the callout side hooks off the telephone set 19, the trunk circuit 11 detects it to activate the transmitters L1, H1 and to call the opposing party. When the receiver 2 detects the callout signal, the incoming display circuit 18 is illuminated for the display of incoming call. When the incoming side hooks off the telephone set, specific 2 tone signals as the response signal is delivered. As mentioned above, the confirmation at the call and response side is made. In case of end of the call, when either of the both hooks on during communication, a given signal is produced from the control section 4 for the side. In this case, the oscillator for H(high tone) and L(low tone) is respectively oscillated with shifted timing. When monitoring this shift at the timing circuit 13, the end of communication can be detected.</p> |
